International journal of sport nutrition最新文献

In a double-blind and randomized manner, 18 male and female junior competitive swimmers supplemented their diets with 21 g.day-1 of creatine monohydrate (Cr) or a maltodextrin placebo (P) for 9 days during training. Prior to and following supplementation, subjects performed three 100-m freestyle sprint swims (long course) with 60 s rest/recovery between heats. In addition, subjects performed three 20-s arm ergometer maximal-effort sprint tests in the prone position with 60 s rest/recovery between sprint tests. Significant differences were observed among swim times, with Cr subjects swimming significantly faster than P subjects following supplementation in Heat 1 and significantly decreasing swim time in the second 100-m sprint. There was also some evidence that cumulative time to perform the three 100-m swims was decreased in the Cr group. Results indicate that 9 days of Cr supplementation during swim training may provide some ergogenic value to competitive junior swimmers during repetitive sprint performance.

The purpose of this study was to investigate the effects of carbohydrate substrate availability on ratings of perceived exertion (RPE) during prolonged submaximal running. Thirty marathon runners were recruited as subjects. A double-blind study design was used in which subjects performed an experimental trial that consisted of a 2.5-hr treadmill run at 75-80% VO2max. During the experimental trial, the subjects in the carbohydrate feeding group ingested a 6% glucose and fructose solution at a rate of approximately 60 g.hr, whereas subjects in the placebo group consumed an equal volume of artificially flavored placebo. Statistical analysis of RPE, respiratory exchange ratio, fat and carbohydrate oxidation rate, and blood glucose concentrations indicated that increased carbohydrate substrate availability attenuated the intensity of exertional perceptions during the later stages of prolonged running at 75-80% VO2max in marathon runners.

The effects of carbonated beverages on sensory acceptability and voluntary fluid intake after exercise were examined. The level of carbonation in a 6% carbohydrate (CHO) electrolyte drink was systematically varied (0, 1.1, 2.3, and 3.0 volumes of CO2), and its impact was assessed in 52 adults following 30 min of exercise. The perception of carbonation intensity closely tracked the differences in physical carbonation levels presented, with all perceived intensities significantly different from each other (p < .01). Overall sensory acceptability, perceived thirst quenching, and perceived sweetness were significantly lower for 2.3-vol CO2 and 3.0-vol CO2 than for 0-vol CO2 and 1.1-vol CO2 (p < .01). Perceived throatburn was significantly higher for 2.3-vol CO2 and 3.0-vol CO2 than for 0-vol CO2 and 1.1-vol CO2 (p < .01). Total fluid intake for 0-vol CO2 and 1.1-vol CO2 was significantly higher than for 2.3-vol CO2 (p < .05), which was significantly higher than for 3.0-vol CO2 (p < .05). It was concluded that levels of carbonation equal to or in excess of 2.3-vol CO2 negatively impact drink acceptability and voluntary fluid intake.

The purpose of this study was to determine the effect of a high vs. a low preexercise carbohydrate (CHO) diet on performance during multiple sets of resistance exercise. Eleven resistance-trained males performed cycle ergometry to deplete quadriceps muscle glycogen stores, followed by 48 hr of a high (HICHO) or a low (LOCHO) CHO diet. Subjects then performed five sets each of squats, leg presses, and knee extensions (resistance = 15 RM) to failure. Blood samples were taken before and during exercise for determination of glucose and lactate (LA). No differences in performance (repetitions x weight lifted) were observed (HICHO = 15,975 +/- 1,381 and LOCHO = 15,723 +/- 1,231 kg). Blood glucose was significantly higher after exercise for HICHO compared to LOCHO (HICHO = 4.8 +/- 0.2 vs. LOCHO = 3.9 +/- 0.2 mmol.L-1). No differences in LA accumulation were observed. The data indicated that preexercise CHO status did not affect resistance exercise performance. Further, the differences in blood glucose and the similarity in LA responses suggest that glycolysis was maintained in the LOCHO condition, and there may have been an increased reliance on blood glucose when preexercise CHO status was low.

The effect of orally supplemented coenzyme Q10 (CoQ10) on plasma CoQ10 concentration and aerobic capacity in endurance athletes was evaluated. Eighteen volunteer male road cyclists and triathletes, 8 in a CoQ10 supplementation group (QG) and 10 in a placebo group (PG), successfully completed the experimental protocol. Subjects were evaluated during and following graded cycling exercise tests, which were performed before and after 28 days of supplementation with 1 mg.kg-1.day-1 of CoQ10 or placebo. The presupplementation plasma CoQ10 concentration was significantly increased from 0.91 +/- 0.13 microgram.ml-1 to 1.97 +/- 0.27 microgram.ml-1 in QG following supplementation (p < .05). However, the CoQ10 supplementation regime had no consistently significant effect on oxygen uptake, anaerobic and respiratory compensation thresholds, blood lactate, glucose and triglyceride kinetics, heart rate, and blood pressure during and after graded cycling to exhaustion.

This randomized, double-blind, placebo-controlled study was designed to determine the influence of vitamin C supplementation on the immune response to 2.5 hr of high-intensity running. Twelve experienced marathon runners (VO2 max 51.6 +/- 1.5 ml.kg-1.min-1, age 40.5 +/- 2.0 years) were randomized into vitamin C (1,000 mg/day for 8 days) or placebo groups. On the test day, subjects ran at 75-80% VO2 max for 2.5 hr, with five blood samples taken before and for 6 hr after. Blood samples were analyzed for cortisol and catecholamines; leukocyte subsets; interleukin-6; natural killer cell activity; lymphocyte proliferation as induced by concanavalin A, phytohemagglutinin, and pokeweed mitogen; and granulocyte phagocytosis and activated oxidative burst. Compared with placebo, vitamin C supplementation had no significant effect on the pattern of change in any of these hormonal or immune measures following 2.5 hr of intensive running.

Beliefs, attitudes, and nutrition resource use among high school wrestling coaches were measured for weight loss, weight class, dehydration, training diet, and eating disorders. Most coaches (82%) considered themselves very knowledgeable about wrestling but less informed about sport nutrition, weight loss, and vitamin supplements. They used a variety of nutrition resources, but only 36% had attended nutrition workshops. Almost all coaches were interested in learning more about specific nutrition topics. More experienced coaches attended nutrition workshops and felt more informed about weight loss and sport nutrition. The mean percentage of correct responses to questions about weight loss was 64%, training diets 59%, dehydration 57%, body composition 52%, and eating disorders 80%; the mean score for healthy attitudes about weight loss was 69%, training diets 34%, dehydration 29%, body composition 70%, and eating disorders 69%. These results can be used to develop training seminars and educational materials to promote greater knowledge and healthy attitudes among wrestling coaches.

This longitudinal study evaluates the relationship of food intake and physical activity with biological maturation of 200 boys and girls during adolescence and young adulthood. The subjects were followed during 9 years from ages 12 to 22 years, with repeated measurements at ages 13, 14, 15, 16, and 21. Biological maturation was estimated four times between ages 12 and 17 as skeletal age by radiographs of the left hand and wrist. Daily nutritional intake (macro- and micronutrients) was assessed with a cross-checked dietary history method. Daily physical activity was assessed through structured interview, whereby average weekly time spent in activity was used to assign a weighted activity score. The 107 girls and 93 boys were divided into three maturity groups: early maturers, late maturers, and average maturers. It was concluded that in both sexes, late maturation seemed to coincide with a higher energetic food intake and a slightly higher activity pattern than early maturation during adolescence.